Evidence has accumulated to suggest that cell surface glycolipids are more highly exposed upon malignant transformation and may therefore act as tumor-specific antigens. Anti-asialo GM1 antibodies, for instance, appear diagnostic for acute lymphocytic leukemia. In the proposed research, monoclonal antibodies will be raised against purified murine tumor glycolipids. These antibodies will be tested for tumor cell specificity and their usefulness in immunotherapy or antibody-directed targeting of antitumor agents. Specifically, glycolipids which I have isolated from cultured P388 leukemia cells, will be complexed separately to bacteria and injected into mice to induce antibody production. Monoclonal antibodies will be obtained by fusing the splenocytes from these mice and plasmacytoma cells, P3-X63-Ag 8.653, and cloning the resultant hybridomas. Hybridomas will be screened for glycolipid specific antibodies and appropriate clones will be injected into mice for monoclonal antibody production. The antibodies will be tested for specificity and cytotoxicity in vitro, using both glycolipid-containing lipid vesicles and various types of whole cells. The binding of the antibodies in tumor cells and non-tumor tissues in vivo will be tested by injecting radiolabeled antibodies into mice bearing P388 ascites tumors. To determine the potential use of anti-glycolipid monoclonal antibodies in drug targeting, one or more of these antibodies will be conjugated to the alkylating agent, chlorambucil and to the toxic A chain of diphtheria toxin (DTA). The conjugates will be tested for retention of antibody specificity in vitro and in vivo, and for in vitro tumor cell killing. Lastly, antibody-chlorambucil, antibody-DTA, and antibodies alone will be tested for effectiveness in tumor cell killing in vivo, as measured by loss of tumor cell viability and increased survival time of tumor-bearing mice. The results of this study will provide evidence on whether the altered glycolipids of tumor cells provide a unique antigenic substrate for the binding of monoclonal antibodies raised against glycolipids. The study may provide a basis for the immunodetection of human malignancies and for cancer immunotherapy or antibody-directed targeting of antitumor agents.